1. Field of the Invention
The invention is directed to a damping valve, particularly for a shock absorber, including a damping valve body with at least one valve seat surface for a valve disk, and a support disk arranged on the valve disk. The support disk has a contour which determines a lever arm up to an effective surface to which pressure is applied to the valve disk by a damping medium, and is pretensioned toward the valve disk by a tensioning plate.
2. Description of the Related Art
A valve disk which is lifted from a valve seat surface by a flow of damping medium is very often used particularly in damping valves for shock absorbers. The effective damping force changes depending upon the length of the lever arm from the damping medium flow to the point of fixation. Comprehensive tests have shown that changes in length in the lever arm of 0.1 mm have drastic effects upon the measured damping force. The valve disk is generally pretensioned in direction of the valve body by at least one annular support disk. Considering that, realistically, the valve seat surface has a certain degree of unevenness, the valve disk is subject to deviations in shape, e.g., during a stamping process, and the tensioning member which pretensions the valve disk on the valve body is also certainly subject to tolerances, the lever arm length mentioned above can not be determined with the desired accuracy. The arrangement of a valve disk with a tensioning element is known, e.g., from DE 44 10 996 C1, to which U.S. Pat. No. 5,615,756 corresponds. The special construction of the piston in the above-cited reference is completely unaffected by the set of problems relating to the fixation of the valve disk and also occurs when the valve bodies are produced by cutting or casting.
Two approaches have been used to solve this problem. First, the tolerances of the individual part were limited to a minimum. In this connection, the permissible surface roughness was also limited because even scoring within the line of tensioning of the valve disk has an influence on the length of the lever arm. Further, parts with a determined dimensional deviation of an impermissible amount were combined with other parts whose tolerance errors were compensated by the former parts. This procedure requires very extensive stocking.
It is the object of the present invention to minimize the deviation in damping force with respect to a desired damping force characteristic in a damping valve.
According to the invention, this object is met in that at least one of the contact surfaces within the line of tensioning is profiled, so that there is a contact circle at the support disk and the radius of the contact circle matches the provided reference dimension for the contour of the support disk determining the lever arm length. The profile contains an unguided cut or free cut that accommodates any inaccuracies in the shape of the structural component parts contained in the line of tensioning.
As a result of this step, the valve disk can now be fixed in a precise manner with respect to diameter, which greatly facilitates maintaining the desired damping force characteristic. The influence exerted by the quality of the surface was reduced to a very great extent by the transmission of force at the contact circle, so that it was possible to manufacture the structural component points in a less refined manner.
In this connection, it is provided that the profile is carried out within the clamping plate or tensioning plate. The tensioning plate offers the most favorable preconditions for shaping the profile, since the valve body can be maintained as a standard part and the support disk is often only very thin.
In a further advantageous construction, the profile is cone-shaped. The support disks have a diameter which is graduated in a defined manner for different damping force characteristics. Depending on the direction in which the cone extends, a cone profile ensures that the inner or outer edge always contacts the profile in the predetermined manner regardless of the diameter ratios of the support disks that are used.
A particularly favorable clamping state of the utilized disks is achieved when the cone angle is less than 1xc2x0. Based on in-house tests, the optimum for the cone angle is achieved from approximately 15xe2x80x2 to 30xe2x80x2. The cone angle depends on the material used for the disks. With a small cone angle of this type, because of the contact circle, in spite of the theoretical line contact, an area contact takes place between the utilized disks which has a positive result on the life of the damping valve.
Further, the tensioning plate forms a stop surface for the at least one valve disk.
It has turned out to be very advantageous when the tensioning plate is produced according to a onetime shaping production method, particularly a sintering method. The desired small cone angle can be obtained more easily.
In addition, the tensioning plate on the side remote of the valve disk can be constructed as a spring plate. The profiled side of the tensioning plate can barely be detected with the naked eye. This could lead to difficulties during assembly. A spring plate can be detected more easily in either manual or automated assembly, so that incorrect installation positions are avoided.
Other objects and features of the present invention will become apparent from the following detailed description considered in conjunction with the accompanying drawings. It is to be understood, however, that the drawings are designed solely for purposes of illustration and not as a definition of the limits of the invention, for which reference should be made to the appended claims. It should be further understood that the drawings are not necessarily drawn to scale and that, unless otherwise indicated, they are merely intended to conceptually illustrate the structures and procedures described herein.